1. Field of the Disclosure
Exemplary embodiments of the present invention relate to a novel metal nanoparticle and a method for forming a conductive pattern using the same. More specifically, exemplary embodiments of the present invention relates to a method for forming a conductive pattern comprising dispersing at least one of metal nanoparticles in an organic solvent and forming a pattern using a printing method wherein the metal nanoparticle has a self-assembled monolayer (SAM) composed of a compound containing a thiol, isocyanide, amino, carboxylate or phosphate group, as a linker, formed on the surface thereof.
2. Description of the Related Art
Materials having a nano-size molecular structure exhibit a variety of electrical, optical and biological properties depending upon one-, two- and three-dimensional space structures and the orders thereof. Therefore, a great deal of research and study has been actively directed to nanoparticles in various application areas including nano-scale materials, optical information electrons, development of biomaterials and the like. Among various types of nano-scale materials, particularly metal nanoparticles have potential applicability in a broad range of areas. This is because, when metals are reduced to a nano-scale size from the bulk state thereof, they will have unique catalytic, electrical, photoelectrical and magnetic properties as the surface area thereof is significantly increased as there are very few metal atoms in nanoparticles. Further, metal nanoparticles, showing conductivity through an electrical conduction mechanism such as charge (or electron) transfer, have a very large specific surface area, and therefore films or patterns containing such nanoparticles may exhibit high conductivity, even at a low content of nanoparticles. In addition, when the packing density of nanoparticles is increased by controlling the particle size thereof to within a range of approximately 3 to 15 nm, it is possible to further enhance the conductivity due to facilitated charge transfer at the metal-metal interfaces.
On the other hand, great advances in the electronic industries have led to a great deal of research and study directed to the development of high-conductivity films or patterns made of various materials. When the metal nanoparticles are employed in the preparation of such conductive films or patterns, there are advantages in that it is possible to prepare high-conductivity films or patterns without sputtering or etching processes involving high vacuum or high temperature conditions and it is also possible to prepare visible light-transparent, conductive patterns by controlling the particle size of the nanoparticles. However, placement of metal nanoparticles into the films or patterns suffers from difficulties associated with the control and arrangement of such fine particles.
As an example of methods for efficient arrangement of metal nanoparticles, methods for using a self-assembled monolayer are known in the art. The self-assembled monolayer is a molecularly arranged structure of a compound containing functional group(s) exhibiting chemical affinity for a certain metal, formed on the surface of the metal nanoparticles, and its thickness can be controlled to the nano-scale, for example, from approximately 10 to 40 nm. In this regard, the formation of the self-assembled monolayer via arrangement of n-alkanethiol on the surface of the metal and the formation of the self-assembled monolayer via arrangement of n-alkanoic acids, dialkyl disulfides and dialkyl sulfides on the surface of the metals such as gold, silver, copper and aluminum have been reported.
However, due to difficulties in controlling of spatial ordering or molecular orientation, and problems associated with instability, defects, surface ordering control and aggregation of the metal nanoparticles on the thin films, occurring when using the metal nanoparticles containing the above-identified self-assembled monolayer, it is not easy to prepare films of a large area or patterns, thereby limiting the commercial application thereof. Further, use of such metal nanoparticles suffers from limitation in the line width which can be achieved via the formation of patterns by means of common photolithography processes and difficulties in the preparation of ultra-fine patterns.
Therefore, there is an urgent need in the art for the development of a novel self-assembling nanostructure which is capable of readily forming large-area films or ultra-fine patterns by means of a simple printing process using metal nanoparticles.